1. Field of the Invention
This invention relates to an optical module and an optical pickup apparatus, and more particularly to an optical module wherein a light emitting element and a light receiving element are integrated and an optical pickup apparatus in which the optical module is incorporated.
2. Description of the Related Art
An optical disc recording and reproduction apparatus uses an optical disc such as a compact disc (CD) including a CD-R (compact disc recordable) and a CD-RW (compact disc rewritable), a digital versatile disc (DVD) or a Blu-ray disc (BD) as a recording medium to carry out recording and reproduction of data. The optical disc recording and reproduction apparatus includes an optical pickup apparatus for optically recording and reproducing data. As the optical pickup apparatus, an optical module or optical integration module is adopted wherein a light emitting element and a light receiving element are integrated in order to satisfy the demand for miniaturization or reduction in thickness. An optical pickup apparatus of the type described is disclosed, for example, in Japanese Patent Laid-Open No. 2007-18583.
In an optical pickup apparatus particularly for use with a BD from among various optical discs, if the light emitting element is not sealed, then an optical characteristic thereof is deteriorated. Therefore, in an optical pickup apparatus for use with a BD, a structure for sealing a light emitting element is adopted in order to maintain the reliability of operation.
FIG. 14 shows an example of a configuration of an optical module adopted in a related optical pickup apparatus. FIG. 15 is a sectional view taken along line A-A of FIG. 14. Referring to FIGS. 14 and 15, a light emitting apparatus 53 is attached to a lower side face of a base plate 51 using a holder member 52. An IC (optoelectronic integrated circuit (OEIC)) chip 54 in which a light receiving element is built is mounted on an upper face of the base plate 51. Further, a hologram lens 56 and a prism 57 which serves as a beam splitter are carried on the upper face of the base plate 51 through a housing 55.
Referring particularly to FIG. 16, the IC chip 54 is electrically connected or coupled to a plurality of electrode portions 58 provided on the upper face of the base plate 51 through wires 59 such as gold wires. The base plate 51 has an opening 60 formed therein for allowing light emitted from the light emitting apparatus 53 to pass therethrough. A flexible printed circuit board (hereinafter referred to sometimes as “FPC substrate”) 61 is attached to the lower face of the base plate 51. The IC chip 54 is bonded to the upper face of the base plate 51 through a bonding layer 62 shown in FIG. 15. The FPC substrate 61 is electrically and mechanically connected to the base plate 51 through solder bonding portions 63. The IC chip 54 has a light receiving portion 64 on a principal face thereof. A plurality of terminal portions 65 for external connection are formed at an end portion of the FPC substrate 61 in the longitudinal direction.
The light emitting apparatus 53 has a CAN package structure. In particular, referring particularly to FIG. 14, a light emitting element 68 is mounted on a block 67 of a heat sink provided on a stem 66 through a sub mount not shown. The light emitting element 68 is sealed with a cap member 69 made of metal and attached to an upper face of the stem 66 in such a manner as to surround the light emitting element 68 and a light extracting window 70 which closes up an opening formed in the cap member 69. A plurality of terminal pins 71 are attached to the stem 66 and electrically connected to the light emitting element 68 by bonded wires or the like.
In the optical module having the configuration described above, light generated from the light emitting element 68 and emitted through the light extracting window 70 of the light emitting apparatus 53 is introduced into the hologram lens 56 through the opening 60 of the base plate 51. The light introduced in the hologram lens 56 passes through the prism 57 and is irradiated upon an external object such as an optical disc. Then, the light reflected by the external object, that is, returning light, is spectralized by the prism 57 and the hologram lens 56 and irradiated upon the light receiving portion 64 of the IC chip 54.
A configuration of another optical module adopted in a related optical pickup apparatus is shown in FIG. 17. Referring to FIG. 17, a recess 72 is formed integrally on a base plate 51, and a light emitting element 74 is mounted in the recess 72 through a sub mount 73 and also an upwardly directing mirror 75 is mounted in the recess 72. The space in the recess 72 in which the light emitting element 74 is mounted is sealed with a transmission window 76 which closes up the opening 60 of the base plate 51 and a lid member 77 which closes up the opposite side of the housing 55 to the opening 60. The remaining part of the optical module is common in configuration to that of the optical module described hereinabove with reference to FIG. 14.
In the optical module having the configuration described above, light emitted from the light emitting element 74 is reflected at the right angle by the upwardly directing mirror 75 and enters the hologram lens 56 through the transmission window 76. Further, the light entering the hologram lens 56 passes through the prism 57 and then is irradiated upon an external object such as an optical disc. Further, the light reflected by the external object, that is, returning light, is spectralized by the prism 57 and the hologram lens 56 and irradiated upon the light receiving portion of the IC chip 54.